The present invention relates to a hydraulic damper, and in particular to a hydraulic damper which is highly suited to a rear cushion unit or a front fork mounted in a two-wheeled vehicle such as a bicycle or a motorbike.
Field of the Invention
In recent years, bicycles, and in particular bicycles which perform off-load running, are being provided with a hydraulic damper as a front fork or a rear cushion unit. Some of these hydraulic dampers can vary the damping force according to a running condition.
However, hydraulic dampers which enable variations of the damping force have a complex construction, have large numbers of parts and demand a large number of assembly steps, thereby leading to increased manufacturing costs and increased weight. Thus, their application particularly to bicycles was difficult.
It is therefore an object of this invention to provide a hydraulic damper which is highly suitable for a front fork or a rear cushion unit of a bicycle, and which permits a damping force to be variably adjusted.
It is a further object of this invention to provide a hydraulic damper which is of simple construction, lightweight and easily fitted to a bicycle.
In order to achieve the above objects the present invention provides a hydraulic damper which comprises an inner tube and an outer tube, one of which is connected to a vehicle body and the other of which is connected to a vehicle shaft. The hydraulic damper comprises a partitioning member provided at the end of the inner tube which divides an internal oil chamber, a damping valve disposed in this partitioning member, a bypass passage disposed in parallel with the damping valve, a control rod which opens and closes the bypass passage, and an actuator installed in the inner tube which controls the control rod, wherein the damping force generated is varied by operating the control rod via the actuator so as to open and close the bypass passage.
The details as well as other features and advantages of the invention are set forth in the remainder of the specification and are shown in the accompanying drawings.